org.apache.johnzon.websocket.internal.lazy.LazySupplier Maven / Gradle / Ivy

Go to download
/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied. See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.johnzon.websocket.internal.lazy;

import java.util.function.Supplier;

public class LazySupplier implements Supplier {
    private Supplier delegate;
    private volatile T instance;

    public LazySupplier(final Supplier provider) {
        this.delegate = provider;
    }

    @Override
    public T get() {
        if (instance == null) {
            synchronized (this) {
                if (instance == null) {
                    instance = delegate.get();
                    delegate = null;
                }
            }
        }
        return instance;
    }

    public T getInstance() {
        return instance;
    }
}